Landfill conduits are increasingly being installed into new and existing solid waste landfills to extract landfill gases and liquids and to inject liquids. Landfill gases principally comprise methane and carbon dioxide, with small amounts of hydrogen sulfide, mercaptan and other trace gases. Landfill liquids typically comprise, for example, landfill leachate or other fluids. Liquids may be injected into landfills to, among other things, increase the biostabilization rates of the landfilled material. The typically horizontal landfill conduits may extend in trenches beneath or within the landfill and are typically perforated to collect landfill leachate and gases. The collected leachate and gases are typically passed to a central location for removal and treatment, for example, burning of the combustible landfill gases. However, these landfill conduits may be susceptible to failure due to becoming obstructed, for example, by an internal build-up of solids or fluids, for instance, becoming “water logged”, that is, the back-up and stagnation of liquids in the conduits and related trenches.
In the past, buried landfill conduits that became obstructed with solids or liquids and became unusable to extract fluids from the landfill and were often abandoned because it was commonly believed that the obstructions in such conduits could not be effectively removed by prior art methods and devices. For example, one prior art method of removing obstructions in buried conduit includes the use of high-pressure water jets, for example, high-pressure rotary turbine cleaning jets. These high-pressure water jets can be effective in removing obstructions from some landfill conduits, for example, leachate lines designed to drain landfill liquids, but such methods are not effective in removing all types of obstructions from landfill conduits. For example, water jets are not effective in removing obstructions from gas extracting leachate lines that become water logged. Typically, water jets simply exacerbate the already undesirable water logging.
Other prior art methods of removing liquids obstructing landfill conduits include vacuum trucks or vacuum tanks that provide a source of vacuum at the terminal end of a landfill conduit. However, the vacuum supplied to the end of the conduit typically dissipates as the vacuum encounters the perforations in the conduit, perforations that may be typically far removed from the source of obstruction. Thus, such terminal vacuum sources are not effective in removing remotely located pockets of fluids, for example, liquids and gases. In addition, gases that are removed by such end-of-pipe vacuum sources may typically be combustible and undesirably provide a potential source of fire hazard or explosion hazard in and around the vacuum truck or vacuum tank.
One other prior art method of removing liquid obstructions in landfill conduits is to insert a pump into the conduit to draw out the obstructing liquids. However, such insertable pumps typically can only remove liquids and cannot effectively remove the mixture of liquid and gases that are typically encountered in such landfill conduits.
Aspects of the present invention overcome these and other limitations of the prior art.